If you manage to keep an infinitely large stack of bills a secret, sure. Once somebody notices and word gets out, I’m doubtful it doesn’t get devalued in a hurry. Since these are bills that we are assuming are valid, it’s going to seem like the central bank is printing money with abandon. Famously not great for public confidence in a currency. Why would I keep my wealth in a currency that somebody has an infinite amount of? They may not be spending it today, but who knows when that changes? I’d certainly be scrambling to convert mine to something else.